Manatee Population

What is the Status of the Manatee Population?

As of the most recent aerial survey flown in February 2015, there are at least 6,063 manatees in Florida. These aerial surveys are flown over manatee aggregation sites during the winter months when manatees gather in high numbers. Since the surveys started in 1991, the number of manatees counted during the surveys had increased, which is related to a growing population, improved survey techniques, and increased knowledge of where manatees aggregate. Synoptic survey counts do not provide statistical estimates of population size and thus are not supposed to be used to determine trends in the population. Rather, these surveys provide a minimum count of manatees. The outcome of the survey is highly dependent on weather conditions and factors including wind speed, glare, and water clarity (turbidity) affect the ability of researchers to count manatees, while the severity of the cold front determines just how many manatees are present at the warm water site to be counted [1].
The manatee population in Florida is divided into four management units (Northwest, Upper St. John's River, Atlantic, and Southwest). Runge et al. (2007) noted that the population of all four units is likely to decrease over the next few decades with the loss of warm water refuges. Currently, the U.S. Fish and Wildlife Service is reviewing updated population and mortality figures, as well as other relevant data regarding threats to manatee habitat, as part of their status review to determine whether manatees should remain listed as an endangered species [2].

[1] Ackerman, B.B. 1995. Aerial surveys of manatees: a summary and progress report. In Population biology of the Florida manatee, edited by T.J. O'Shea, B.B. Ackerman, and H.F. Percival, 13-33. Information and Technology Report 1, U.S. Department of the Interior, National Biological Service.